How Much Does It Cost To Win A Senate or Congressional Seat?

This election cycle, an average winning Senate candidate had spent $10.4 million through Oct. 19 (reflecting the latest reports filed with the Federal Election Commission). That’s a $1.8 million increase over the same period in the 2014 cycle. By the end of last cycle, the number rose to $10.6 million, and a similar uptick is expected this time once post-election and year-end reports are filed.

But in the post-Citizens United era, spending by campaigns alone doesn’t tell the whole story. Factoring in outside spending (excluding outlays by party committees) nearly doubles the average cost of winning a Senate seat to $19.4 million, which tops the $16.8 million average cost by the end of 2014 cycle.

The role of super PACs and political nonprofits in Senate races has only grown since 2012. Four years ago, 22 percent of the $14.6 million total average cost of winning a Senate seat came from outside groups, and in 2014, their share was 37 percent of the $16.8 million. This time around, the share has jumped to 47 percent.

Outside spending less a factor in the House

An average winning House candidate had spent $1.3 million through Oct. 19 this cycle, on par with with the $1.2 million such a candidate spent over the same period in 2014 and 2012. The numbers rose to $1.5 million and $1.6 million by the end of the 2014 and 2012 cycles, respectively.

Outside groups are a relatively unimportant factor in most House races, unlike in the Senate. Their share of the average cost of winning in the House has been relatively steady: Of the $1.5 million total average cost of winning a House seat including outside spending this cycle, 14 percent came from outside groups, a relatively small increase from 2014’s 11 percent.